1. Field of the Invention
This invention relates a mechanical supercharger utilized in internal combustion engines, and more particularly to a mechanical supercharger wherein a relief valve is accommodated.
2. Description of the Related Art
It is well known that a relief control valve may be generally adopted to control supercharging pressure in a mechanical supercharger. In a conventional supercharger with a relief control valve, as shown in FIG. 1, a surge tank 22 is connected with an intake manifold 21 of an internal combustion engine 20. A relief valve 23 is disposed in the surge tank 22 so as to keep a suction air pressure in surge tank 22 under a predetermined value. The relief air from relief valve 23 is returned to an upstream portion of the supercharger 24 or to an air cleaner 27 via a control conduit 25 that is separate from the supercharger 24. Numeral 26 indicates a carburetor.
In the above-mentioned conventional relief control method, however, since the control conduit 25 is positioned outside of supercharger 24 and the construction of relief valve 23 is complicated, there is a drawback that the device has a large size. Furthermore, in the conventional mechanical supercharger, noises are generated by discharge pulsation of the supercharging pressure released from the relief valve. In addition, when the control conduit is disposed on the outside of the supercharger, there is a noise problem in that a radiating noise is released from the control conduit. When the mechanical supercharger 24' is located in the downstream portion of the carburetor 26 as shown in FIG. 1, there will be a further problem in that gasoline fuel can leak out from the joints of control conduit 25.